It has become quite popular to use online storage for “anywhere-access” to data and easy synchronization. In some configurations, this is referred to as “cloud storage.” In most cases where individual persons, organizations and/or companies want to securely store their data, there is some authentication needed for access to the data and authentication can be in the form of an access key such as a password.
As used herein, “user” can refer to individual persons, organizations, companies, entities or the like, be they humans using computer interfaces or computers using computer interfaces, that desire or need to store data in online storage. “Online storage” refers to storage that is accessible from more than one location or device via a network or other electronic communications medium. In many cases, the online storage is partitionable, so that more than one user can access their distinct partitions. So that authorized users can access a given partition of online storage and unauthorized users cannot (in most cases that are within security expectations) access that partition, some sort of access control is provided. “Access” can include the ability to read data from the partition, write data to the partition, modify data in the partition, possibly also reading, writing, and/or modifying metadata about the data and to delete data/metadata. The stored data can be in the form of data records, files, blobs or other data structures. Access might also be to resources other than just data, such as computing equipment, cloud computing capabilities, network-connected devices (printers, other equipment), money, the ability to control a transaction, etc.
Access to a partition (or even to online storage elements as a whole) might be controlled by a server, router, device, software, etc. that decides whether to allow access to particular users. Partitions might be hard coded (e.g., each user has a fixed 100 MB portion of memory managed on the storage server) or just logically partitioned (e.g., each user can upload some number of photos, up to some designated limit, onto a photo album server and those uploaded photos are associated with the user who/which uploaded them).
Access might be determined by the controller based on authentication—wherein a particular user uses a computing device or other input means to identify to the controller that the user is actually that user and not a hacker, poser or unauthorized person (which may be someone within the company running the controller and cloud servers or someone outside the company). One method of authentication is to assign or generate an access key, provide the access key to an authorized user with the understanding that each authorized user will not share the access key with an unauthorized user, so that the controller can assume that a user is authorized if the user proves access to the access key.
In recent years, the Internet and especially the Web (the collection of HTML and similarly formatted, possibly interlinked set of documents that are typically accessed using a browser or app or similar tool, over a network or storage element), has become an important media, present in the daily life of a majority of people and useful for interfaces to online storage. These services often require user authentication, requiring entering of a username and a password to allow access to the customer account for each service, including personal and confidential data.
A very specific example is an online file storage server that controls access using passwords and is accessible through the Internet. The storage server might maintain a list of users and the file areas they are allowed access to, and the user list might include the passwords of all of the users. Then, when someone connects over a public Internet connection to the storage server and attempts to access a particular file, the server could hold off on the request until the user provides a user identifier (such as a “username”) and a password. Once those are provided, the storage server looks up the username in the user list, checks the provided password against the password stored in the user list for that user and if the passwords match, the storage server then looks up in the user list to determine what partitions or files the user has the authority to access, and serves the requested content/file/data to the user if the requested content/file/data is within that user's authority.
There are a number of known problems with this approach. First, it is often an expectation of users that their online storage is accessible only to them and not necessarily to employees of the company or entity that operates the online storage server. This expectation is not met if those employees have ready access to user passwords, as then they would be able to pose as those users, typically outside the scope of their actual employment responsibilities. Also, if an interloper is able to watch network traffic, the interloper may be able to grab usernames and passwords, thereby violating the security assumption that only authorized users will have access to secured data.
One partial solution that has been in use is to eliminate the storage of passwords at the storage server and instead just store hashes of passwords. A “hash” of some data item is a function of that data item that is “one-way” in that computing the data item having only the hash of it is considerably harder (or perhaps impossible) than computing the hash having only the data item.
In a hash-based storage system, the data to be stored on the storage server is encrypted using the user's password and the encryption is done at the user's local device. Examples of local devices are computers, laptops, smart phones, tablets, and other computing devices under local control of the user. When the data is initially sent to the storage server to be written to the user's partition, it is sent already encrypted and the user also provides a hash of the user's password. Of course, this might all be done behind the scenes by client software that simply asks a user to specify the file to upload and does the rest.
In any case, the storage server stores the encrypted data and the hash of the user's master password used to encrypt the data. Later, when the user wants to read or download that data, the user supplies the user master password to the storage server, the storage server computes the hash (or perhaps the hash of the password is created at the user's side and sent to the storage server), compares it to the stored hash, and if there is a match, it serves the requested file to the user's client software so the user can have the data locally. The client software may also automatically decrypt the served data, again using the master password.
While this is better than straight storage of master passwords in the clear at the storage server and transmission of the data when the storage server handles the encryption/decryption, there are still problems. When the master password is used both for authentication to the server and for data decryption, the master password will typically be stored on the server. This can create problems, because if the user list is hacked into by unauthorized agents, or accessed by a sabotaging employee, many passwords can be compromised. Even where only the hashes are stored, there is a risk, because with enough time and computing power, an unauthorized agent can run analysis on tables of password hashes to guess weak passwords that would hash to the values stored in the password hash table.
Thus, there is a need for a more secure storage and online access solutions, especially where the data being stored is of a sensitive nature.